Live head lice are tiny tan or grayish insects, roughly 2 to 3 millimeters long, about the size of a sesame seed. They have six legs, each tipped with a hook-like claw designed to grip hair, and they move exclusively by crawling. If you’re checking someone’s head and wondering what you’re looking at, here’s how to identify lice at every stage.
What Adult Lice Look Like
An adult louse is flat, oval-shaped, and tan to grayish in color. At 2 to 3 mm, it’s small enough to miss at a glance but visible to the naked eye if you know where to look. Adult lice feed on blood from the scalp, which can make their bodies appear slightly darker after a meal. They have no wings and cannot jump or fly. Each of their six legs ends in a curved claw that hooks onto individual hair strands, allowing them to hang on tightly and crawl along the shaft down to the skin.
Lice move at less than four inches per minute, so they aren’t fast. But they’re good at staying close to the scalp where it’s warm, which makes them easy to overlook during a casual check. You’re most likely to spot them at the back of the head, along the neckline, and near the ears.
What Nymphs Look Like
Nymphs are baby lice that have recently hatched. They look like smaller versions of adults, with the same body shape and six legs, but they can be harder to see because of their size. A freshly hatched nymph is roughly the size of a pinhead. Nymphs also feed on blood from the scalp and grow into full adults about a week and a half after hatching. As they mature, they go through several molts, getting slightly larger each time until they reach adult size.
What Nits Look Like
Nits are lice eggs, and they’re the most commonly spotted sign of an infestation because they don’t move. They’re tiny ovals, usually yellow or white, and they attach firmly to the hair shaft very close to the scalp. A female louse uses a glue-like substance to cement each egg in place, which is why nits don’t slide or fall off when you run your fingers through the hair.
Nits that are close to the scalp (within about a quarter inch) are typically viable, meaning a nymph will eventually hatch from them. Nits found farther from the scalp have usually already hatched or are no longer viable. The empty shells stay stuck to the hair and grow out with it over time, which is why you can sometimes find them an inch or more from the scalp long after treatment.
Lice vs. Dandruff
This is one of the most common points of confusion. Dandruff flakes are white or yellowish, irregularly shaped, and sit on the scalp itself. The key difference: dandruff falls off easily when you shake or brush the hair. Nits do not. They are glued to the hair strand and resist flicking, brushing, or even pulling. If you can easily slide a white speck off the hair with your fingers, it’s almost certainly dandruff or other debris. If it’s stuck fast and has a teardrop or oval shape, it’s more likely a nit.
Another distinction is location. Dandruff is visible on the scalp surface, while nits are attached to individual hairs. Looking at the particle under good lighting or with a magnifying glass can help you tell the difference.
How to Spot Live Lice
Because lice stay close to the scalp and avoid light, the best way to find them is with a fine-toothed lice comb (sometimes called a nit comb) and good lighting. Wet the hair first, which slows the lice down and makes them easier to catch. Part the hair into small sections and comb from the scalp outward, wiping the comb on a white paper towel after each pass. Live lice will show up as small tan or gray specks that move.
Focus your search on the areas behind the ears and along the back of the neck, where lice congregate most. Itching is a common symptom, but not everyone with lice feels itchy, especially during the first few weeks of an infestation. So a visual check with a comb is more reliable than waiting for scratching to start.
What Lice Cannot Do
Unlike fleas, lice cannot jump. They also cannot fly or swim. They spread almost exclusively through direct head-to-head contact, which is why they’re so common among young children who play closely together. Lice don’t survive long off a human host, typically less than one to two days, because they need frequent blood meals from the scalp. Finding a louse on a pillow or hat is possible but uncommon, and that louse is unlikely to survive long enough to start a new infestation on its own.